Synthesis and catalytic applications of novel Palladium PEPPSI complexes

Abstract

In this work, a series of novel Pd PEPPSI complexes bearing symmetrical and unsym¬metrical NHC ligands were synthesized and fully characterized using 1H and 13C NMR spectroscopies. The crystallographic structures of three complexes were also determined using single crystal X-ray diffraction analysis. The catalytic activity of six out of the ten complexes obtained was assessed toward the Suzuki-Miyaura cross-coupling and the Heck reaction of aryl bromides with phenylboronic acid and styrene, respectively. All the complexes led to high yields of biphenyl derivatives with all the substrates tested in the Suzuki-Miyaura cross-coupling whether they bore electron-donating or electron-withdrawing substituents. They also gave excellent results for the coupling of aryl bromides bearing electron-withdrawing groups with styrene in the Heck reaction, but failed to efficiently couple an aryl bromide bearing a 4 methoxy electron-donating group with styrene.